Rotary expansible drill bits



Dec. 9, 1958 A. w. KAMMERER 2,863,641

ROTARY. EXPANSIBLE DRILL BITS Filed Jan. 24, 1956 2 Sheets-Sheet 1 Dec. 9, 1958 A. w. KAMMERER ROTARY EXPANSIBLEI DRILL BITS 2 Sheets-Sheet 2 Filed Jan. 24, 1956 BY g flrrae aa United States Patent norARY EXPANSIQBLE DRILL BITS Archer W. Kammerer, Fullerton, Calif., assignor of onefifth to Archer W. Kammerer, Jr., and one-fifth to .lean K. Lamphere, both of Fullerton, Calif.

Application January 24, 1956, Serial No. 561,098 14 Claims. (Cl. 255 -76) The present invention relates to rotary drill bits, and more specifically to drill bits of the expansible type capable of drilling or enlarging bore holes below a string of well casing to a greater diameter than the inside diameter of the casing string through which the bits are moved.

Certain types of rotary drill bits of the expansible type embody a mandrel slidably splined to the main body of the tool and movable relative to the tool body to a position in which the cutters are held in their outwardly expanded condition. Sand and other foreign substances in the drilling mud being pumped through the bit may pack between the mandrel and the bit body, and may tend to prevent the required relative movement therebetween.

If expansion of drill bit cutters is accomplished hydraulically, sand and other foreign substances in the drilling fluid might pack or accumulate in the hydraulically actuated portion of the rotary drill bit, and may prevent proper subsequent retraction of the cutters when the tool is to be removed from the well bore. Assuming that the cutters are retracted, the foreign substances can still impose difiiculties in the way of dismantling and cleaning the tool, and can create excessive wear on the parts.

It is an object of the present invention to prevent sand, debris, and other materials, from accumulating between the mandrel and body of the tool, insuring freedom of relative movement between such parts.

Another object of the invention is to prevent sand, debris, and other relatively solid materials, from accumulating in the hydraulically actuated portions of a rotary expansible drill bit. If the hydraulically operated bit is of the type in which a mandrel is slidably splined to the main body of the tool, the preventing of the foreign substances from accumulating insures the free relative movement between the mandrel and the body.

This invention possesses many other advantages, and has other objects which may be made more clearly apparent from a consideration of a form in which it may be embodied. This form is shown in the drawings accompanying and forming part of the present specification. It will now be described in detail, for the purpose of illustrating the general principles of the invention; but it is to be understood that such detailed description is not to be taken in a limiting sense, since the scope of the invention is best defined by the appended claims.

Referring to the drawings:

Figure l is a longitudinal section through an embodiment of the invention disposed in a well bore, with the cutters and other parts in their initial retracted positions;

Fig. 2 is a longitudinal section similar to Fig. 1, disclosing the cutters locked in their fully expanded position;

Fig. 3 is an enlarged cross-section taken along the line 33 on Fig. 1;

Fig. 4 is an enlarged cross-section taken along the line 44 on Fig. 2;

Fig. 5 is a cross-section taken along the line 5-5 on Fig. 2;

Fig. 6 is an enlarged longitudinal section taken generally along the line 66 on Fig. 4.

As shown in the drawings, a rotary expansible drill bit A is secured to the lower end of a string of drill pipe B extending to the top of the well bore C, and by means of which the drill bit is lowered through a string of well casing D to a region therebelow where the hole enlarging operation is to commence. The general type ,of expansible drill bit disclosed in the drawings is shown and described in Patent No. 2,545,036, to which attention is invited for certain structural details.

The upper portion of the rotary drill bit consists of a mandrel 10 having an upper pin 11 threadedly connected to a sub 12 forming the lower end of the string of drill pipe B. This mandrel includes an upper kelly or drill stem 13 slidably splined to the main body 14 of the drill bit. The exterior 15 of the lower portion of the kelly is non-circular in shape, being telescopically received in a companion non-circular socket 16 provided in the main bit body, the kelly 13 being capable of moving longitudinally with respect to the body 14 and also being capable of transmitting rotary movement thereto.

The mandrel 10 has a limited range of longitudinal movement within the body 14, its downward movement being determined by engagement of the lower end 17 of the kelly with an inwardly directed body shoulder 18, and its upward movement being limited by engagement of an external shoulder or piston portion 19 of the kelly with one or more stop rings 20 that may be split to enable them to be inserted within an internal groove 21 in the main body of the bit, the stop rings extending into a cylinder space 22 formed between the kelly or drill stem 13 and the body 14 of the tool. It is to be noted that the coengageable surface of the lower end 17 of the kelly and the inwardly directed body'shoulder 18 are frusto-conical in shape, tapering in a downward and inward direction, in order that the engagement of the lower end of the kelly with the shoulder will tend to center, and insure the retention of, the kelly 13 in a central and coaxial position, within the body 14 of the tool.

The body 14 has a plurality of expansible parts mounted on it. These include cutter supporting members 23 pivotally mounted in body slots 24 on hinge pins 25 suitably secured to the body to prevent their loss therefrom. Each cutter supporting member 23 has a leg portion 23a depending from the hinge pin 25 and terminating in a bearing supporting pin 26 inclined inwardly and downwardly. A side roller cutter 27 is rotatably mounted on each bearing supporting pin 26, being mounted upon anti-friction roller'and ball bearing elements 28, 29 rollable on the bearing supporting pins. The ball bearing elements 29 serve to lock the cutter 27 against endwise movement on the bearing supporting pin 26, as well as to transmit axial and radial thrusts, the roller bearing elements 28 transmitting primarily radial thrusts. The manner of mounting the ball and roller bearing elements 29, 23 between the cutter 27 and bearing supporting member 26 is specifically described in the above-mentioned Patent No. 2,545,036, to which attention is invited.

Each cutter supporting member 23 and cutter 27 tend to occupy a retracted position substantially entirely within the confines of the main body 14 of the bit. These cutter supporting members and their cutters are expanded outwardly to enlarge the sides of the well bore C and to operate upon a formation shoulder E that the cutters form in the latter. To accomplish the'expansion, each cutter supporting member 23 has an inclined expander surface 39 on its inner portion 31 below the hinge pin 25 which tapers in a downward and inward direction. Each expander surface merges smoothly into and terminates in a lock surface 32 formed on a lock portion 33 of the cutter supporting member. The outward expansion is accomplished by producing relative longitudinal movement between the mandrel 10 and the bit body 14, which will produce the relative longitudinal movement between the cutter supporting members 23 and a tubular member 34 of the mandrel. This tubular member 34 includes a lower portion 35 slidable within a guide 36 secured to the body 14 and extending across the body slots 24. This guide is disposed below the lock portions 33 of the cutter supporting members 23.

Located initially substantially above the guide 36 and below the hinge pin 25 and in cutter member recesses 37 is a mandrel lock and expander 38 which has outer surfaces 39 adapted to engage the expander surfaces 30 and the lock surfaces 32. The lock and expander 38 may be formed integral with the tubular member 34, the

upper end of the latter being piloted within a socket 40 formed in the lower portion of the kelly 13. An enlarged boss 41 on the tubular member engages a downwardly facing shoulder 42 of the kelly, the tubular member being held against this shoulder by a suitable split retainer or lock ring 43 snapped into an internal groove 44 encompassing the Kelly socket 40 and engaging a downwardly directed shoulder 45 formed on the tubular member boss 41.

To facilitate passage of drilling or other fluid down through the central passage 46 of the kelly or drill stem 13 and into the central passage 47 extending completely through the tubular member 34, the latter has a portion 48 extending upwardly from its boss 41 and provided with an upwardly flaring end 49 merging smoothly into the lower tapered surface 50 of the kelly passage 46. Leakage of fluid around the exterior of the tubular member 34 is prevented by a suitable side seal ring 51, such as a rubber O ring, located in a peripheral groove 52 in the boss 41, which engages the wall of the Kelly socket 40.

Assuming that the body 14 of the tool is elevated relatively along the tubular mandrel It), the inclined expander surfaces 39 of the cutter supporting members 23 will be shifted upwardly along the lock and expander portions 38 of the tubular member. During such upward shifting, the cutter supporting members 23 and the cutters 27 carried thereby will be pivoted about the hinge pins 25 and urged in an outward direction. The upward movement of the body 14 with respect to the tubular mandrel it can continue until the cutters 27 have shifted outwardly to their fullest extent, as determined by engagement of stop shoulders 53 on the cutter supporting members with companion shoulders 54 formed in the body on opposite sides of the body slots 24. When such engagement occurs, the lower end 17 of the Kelly portion of the tubular mandrel It will engage the body shoulder 18, and the lock and expander 38 on the tubular member 34 will be disposed behind and in engagement with the lock portion 33 on the cutter supporting members 23.

It is to be noted that the surfaces 32 of the lock portions of the cutter supporting members 23 and the conpanion surfaces 39 on the lock and expander portions 38 of the tubular member are substantially parallel to the axis of the drill bit when the cutters are fully expanded, to prevent the reactive forces of the formation on the cutters 27 from moving the latter inwardly. As a practical matter, it is preferred that the co-engaging lock surfaces 32, 39 be inclined slightly in a downward direction toward the axis of the tool, to insure release of the lock and expander portion 38 from the cutter supporting members 23 when the latter and the cutters 27 are to be shifted to a retracted position.

In the specific form of the invention disclosed in the drawings, the relative longitudinal movement between the tubular mandrel 10 and body 14 of the tool is accomplished hydraulically. Thus, the piston or enlarged portion 19 on the drill stem 13 is received within a counterbore formed on the upper portion 14a of the body 14 of the tool. This upper portion 14a actually constitutes a cylinder having a cylindrical wall 61 extending from a lower shoulder 62, defining the bottom of the counterbore, to an upper head and guide 63, which has a depending portion 64 inserted in the upper end of the cylinder and releasably retained therein by a split snap ring 65 carried in a groove in the cylinder portion 64 and adapted to be received within a generally V-shaped internal groove 66 in the upper portion of the cylinder wall 61. The head 63, with the snap ring 65 therein, need merely be forced into the cylinder 14a, and when located opposite the V-shaped groove 66, the snap ring will expand inherently partially into the latter to releasably lock the cylinder head 63 to the cylinder 14a.

The confined cylinder space 22 is formed between the piston portion 19 of the kelly 13, the periphery of the kelly above the piston, and the cylinder 14a. A suitable packing or side seal ring67 may be disposed in a suitable piston ring groove 68 formed on the piston 19, which is adapted to slidably seal against the cylindrical wall 61 of the cylinder 14a. Fluid is thereby prevented from passing in a downward direction between the piston 19 and the cylinder 14a. Similarly, fluid is prevented from passing in an upward direction out of the annular cylinder space 22 by a cylinder packing or sealing structure 69 secured to the cylinder 14a and slidably engaging the periphery of the kelly 13. This structure may take any suitable form. As disclosed, it consists of a lower packing supporting ring 70 resting upon the split retainer rings 24) received within the internal groove 21 in the cylinder 14a. A non-metallic packing 73, which may be made of any suitable material, rests upon the ring 70, with its upper end engaging an upper backing ring 74 bearing against a split retainer ring 75 received within an internal groove 76 in the cylinder 14a. The outer upper portion 75a of the retainer ring 75 and the adjacent upper wall of the internal groove 76 are preferably inclined in an upward and inward direction, in order that the split retainer ring 75 will be forced inwardly out of the groove 76 when it is subjected to a sufficient upwardly directed longitudinal force. It is evident that the upper and lower split retainer rings 75, 2t} prevent longitudinal movement of the packing structure 69 with respect to the bit body cylinder the non-metallic packing portion 73 of the sealing structure 69 engaging the cylinder wall 61 to prevent leakage therealong, and also slidably engaging the periphery of the drill stem portion 13 of the tubular mandrel 10.

Fluid under pressure in the string of drill pipe B and in the tubular mandrel 10 can be fed into the cylinder space 22 through one or more side ports 77 establishing communication between the central passage 46 through the kelly 13 and the cylinder space. Such fluid under pressure is developed in the form of invention disclosed in the drawings by virtue of the fact that the passage 47 through the tubular member 34 of the mandrel is of a restricted diameter as compared to the passage 46 through the Kelly portion 13 of the mandrel. As a result, the pumping of drilling mud, or other fluid, at an adequate rate through the passage will build up a back pressure of fluid in the passage 46, which pressure will be imposed on the fluid in the cylinder space 22 acting upon the packing structure 69, to urge the body 14 of the tool in an upward direction with respect to the tubular mandrel 10, to secure the outward expansion of the cutter supporting members 23 and cutters '27 to their fullest extent.

For the purpose of securing the proper cooperation between the tubular mandrel and the body 14 of the tool, the slidable spline connection 15, 16 therebetween must be made accurately. Byvirtue of the specific structure disclosed in the drawings, a slidable spline connection is provided which insures the coaxial relation between the tubular mandrel and the body of the tool, while insuring the transmission of large torques between them during the performance of the hole enlarging operation. As described above, the lower portion of the kelly 13 is non-circular in cross-section, and this is also true of the companion socket 16 formed in the body 14 of the tool above its lower tapered shoulder 18. Actually, the non-circular configurations described above lie partially on sections of circles, to enable the desired coaxial relationship to be obtained between the parts (Fig. 3).

Thus, the exterior 15 of the lower part of the kelly is first formed with a cylindrical shape 80, the cylinder having the required external diameter. Similarly, the socket 16 in the body, whichlies between the counterbore shoulder 62 and the lower stop shoulder 18 on the body, is also bored out to provide a cylindrical wall 81 having the requisite diameter, which is only greater than the external diameter of the Kelly surface 80 sufiicient to provide the necessary working clearance between these parts. Opposite portions of the lower Kelly region are then flattened, as by milling away the material, to provide the opposed flat sides 82. Companion flat surfaces 83 are provided in the body socket. Specifically, such flat surfaces are formed on opposed wear members or shoes 84 of segmental shape having arcuate outer surfaces 85 of a curvature conforming to the inner wall 81 of the socket 16. These wear members 84 are integrated to the body 14 of the tool by providing lateral holes 86 through the wall of the body through which welding material 87 can be deposited, to firmly secure the wear members to the body of the tool. The wear members 84, of course, extend from the'lower end of the counterbore 60 substantially to the lower shoulder 18 of the body 14.

When the rotary expansible drill bit A is run in the well casing D, with the cutter supporting members 23 and the cutters 27 in their initial retracted positions, the wall of the well casing D will prevent the outward expansion of the cutters 27, the supporting members 23 merely sliding along the casing wall during descent of the apparatus. When the apparatus has been lowered below the casing shoe F, the pumps at the top of the well bore are started, to pump fluid at a sufiicient rate through the drill pipe B and the tubular mandrel passage 46, 47. Pumping of the fluid builds up a back pressure in the Kelly passage 46 and in the fluid in the ports 77 and cylinder space 22, which pressure will act upon the cylinder packing structure 69, to urge the body 14, the cutter supporting members 23 and cutters 27 in an upward direction with respect to the mandrel 10.

During such upward movement, the upper ends of the expander surfaces 30 on the cutter supporting members 23 are brought to bear against the lock and expander portion 38 of the mandrel, the cutters 27 being urged in an outward direction against the wall of the well bore C. The drill pipe B and the rotary drill bit A are rotated at the proper speed, while fluid is being pumped through the apparatus, the cutters 27 enlarging the well bore without the drill pipe being moved vertically. As the cutters enlarge the well bore, the hydraulic force acting upon the body 14 raises the latter, the cutter supporting members 23, and the cutters 27 to a further extent, to further expand the cutters outwardly. Eventually, the cutter supporting members and cutters will be shifted outwardly to their maximum extent as determined by engagement of the supporting member stop shoulders 53 with the companion body stop shoulders 54, and the engagement of the body shoulder 18 with the lower end 17 of the Kelly portion 13 of the tubular mandrel 10. As explained above, with the parts in this position, the lock portion 33 of the cutter supporting members 23 will bear against the lock and expander portion 38 of the tubular member 34, to preclude inadvertent partial retraction of the cutters 27 from their fully expanded position.

Downweight of the proper amount can now be imposed on the string of drill pipe B, this downweight being transmitted through the kelly 13 to the body shoulder 18 and from the body through the stop shoulder 54 directly to the cutter supporting members 23 and the cutters 27, urging the teeth of the latter into the transverse formation shoulder E previously produced, in order to drill away the formation shoulder and enlarge the Well bore to the required diameter and along a desired length of hole. During the imposition of such downweight on the apparatus, the tapered surface engagement'between the lower end 17 of the kelly 13 and the body shoulder 18 will insure the coaxial position of the mandrel 10 with respect to the body 14 of the tool.

In the event it is desired to retrieve the apparatus A from the well bore after the hole enlarging operation has been completed, or as a result of the cutters 27 becoming worn, it is only necessary to discontinue the pumping of the drilling fluid through the drill pipe B in the apparatus, to relieve the pressure in the cylinder 14a, and to elevate the drill pipe. Such elevating movement will elevate the tubular mandrel 10 with respect to the body 14 and the cutter supporting member 23, to raise the lock an expander portion 38 above the expander surfaces 30, whereupon the cutters 27 can drop back to their retracted position. In the event the cutters are reluctant to move to their retracted position, the outer surfaces of the cutter supporting members 23 will engage the casing shoe F, which will then force them inwardly, whereupon the apparatus can be withdrawn through the Well casing D to the top of the hole.

For the purpose of forcibly retracting the cutter supporting members 23 and cutters 27 without the necessity for their engaging the casing shoe F, and to hold the cutter supporting members and cutters in such retracted position, the tubular member 34 of the mandrel is provided with an enlarged portion above its expander 38 having an upwardly facing shoulder 96 adapted to engage downwardly facing surfaces 97 on relatively short arms 23]) on the cutter supporting members 23 extending laterally inward from the fulcrum pins 25. Following the relieving of the hydraulic pressure within the apparatus, and the elevation of the mandrel it) with respect to the body 14, the expander and retainer 38 is moved upwardly along the cutter supporting members 23, to allow the latter to drop back to their retracted position under the action of gravity. In the event the cutter supporting members do not retract by themselves to the fullest extent, then the upwardly facing shonlder 96 on the tubular member will engage the arms 2% on the cutter supporting members, to swing them in an upward direction and thereby swing the depending leg portions 23:: and the cutters 27 inwardly of the apparatus. During the elevation of the apparatus in the well bore, the shoulder 56 on the mandrel will be engaging the cutter supporting member arms 23b steadily, exerting a continuing upward force therein tending to hold the leg portions 23a of the cutter supporting members 23 and the cutters 27 in their full inward positions.

During the outward expansion of the cutters 27, the fluid pumped down through the mandrel passages 46, 47 discharges from the lower end of the mandrel member 34 and sometimes tends to pass upwardly around the tubular member 34 and into the non-circular socket 16 in the main body 14 of the tool. Such fluid also tends to move upwardly between the non-circular portion of the kelly and the socket of the tool and into the counterbore 60. Sand, debris, and other relatively solid materials in the drilling fluid may settle out in the counterbore, the settlings being supported by the lower end 62 of the counterbore, effecting an accumulation or packing of relatively solid materials between the lower end of the piston 19 and the counterbore shoulder 62. Such accumulation of materials impedes and may, in fact, prevent full elevation of the body 14 along the mandrel 10, to insure complete expansion of the cutters 27 and their being locked in their outwardly expanded position. The foreign materials in the drilling mud may also tend to bind between the wall 81 of the socket 16 and the exterior of the lower Kelly portion, tending to impede relative longitudinal movement between the body 14 and mandrel 10.

In the present instance, the tendency for foreign materials to pack or bind between the lower portion of the kelly 13 and the body of the tool is minimized to a considerahle extent by providing circumferentially spaced longitudinally extending grooves 100 in the arcuate portions of the kelly, such grooves extending from the piston 19 of the kelly and opening downwardly through its lower end 17.

It has been found that accumulations of sand and other foreign materials in the counterbore 60 between the piston 19 and the shoulder 62, as well as between the lower portion of the kelly 13 and the wall 81 of the socket 16, are prevented by providing an upper set of circulation ports or passage 101 through the body of the tool and opening into the counterbore 60 immediately above its shoulder 62. In addition, a lower set of circulation ports 102 is provided through the body of the tool immediately above the tapered shoulder 18, which provides communication between the socket 16 of the body and its exterior. With the provision of such ports 101, 102, some of the circulating fluid being pumped down through the mandrel and out through its lower end flows upwardly into the socket 16 and then out through the lower ports 102. Moreover, it flows upwardly between the lower portion of the kelly and the wall 81 of the socket and into the counterbore 61. Any debris, and the like, that might be present in the fluid can then pass outwardly with it through the upper set of ports 101, the fluid then flowing upwardly around the cylindrical portion 14a of the body and back to the top of the hole. Such flow of fluid prevents any accumulation in the counterbore 61 from building up upon the counterbore shoulder 62, which would tend to prevent the relative upward movement of the body 14 with respect to the mandrel 10, and thereby prevent full outward expansion of the cutters. As the body 14 moves upwardly, any solid particles that might have accumulated immediately below the piston 19 of the mandrel are placed in line with the upper circulation ports 101 and are then flushed outwardly therethrough.

When the body 14 of the tool has been elevated along the mandrel 10 to the fullest extent, in which the tapered shoulders 17, 18 coengage, the upper and lower sets 101, 102 of circulation ports are still eflective to insure against the presence of foreign substances between the lower Kelly portion 80, 82 of the mandrel and the body 14. The circulating fluid pumped down and discharged from the mandrel 10 passes upwardly around the exterior of the body 14, some of this fluid flowing in through the lower circulation ports 102 into the space between the lower portion of the kelly and the body socket wall 81, continuing upwardly therebetween and then discharging through the upper circulation ports 101. To facilitate such circulation, the piston portion 19 of the mandrel is provided with an intermediate peripheral groove 103 which will be in alignment with the upper circulation ports 101 when the mandrel and body shoulders 17, 18 contact, the lower end 190 of the piston 19 being spaced slightly above the counterbore shoulder 62, and the lower portion of the piston between the groove 103 and its lowermost end 1% being provided with a plurality of circumferentially spaced longitudinal grooves 104. In this manner, a relatively free passage exists from the lower circulation ports 102 through the longitudinal grooves 100 in the mandrel and the clearance space between the kelly and the wall' 81 of the socket, through the space between the lower end 19a of the piston and the counterbore shoulder 62, through the longitudinal grooves 104 in the lower piston portion to the peripheral piston groove 103, from where the fluid and any substances contained therein can pass outwardly through the upper circulation ports 101.

It is found that with the arrangement described, accumulation of sand and other debris between the lower Kelly portion of the tool and the body of the tool does not occur, the body and mandrel having freedom of relative longitudinal movement.

During the pumping of the drilling fluid through the Kelly passage 46, the fluid under pressure passes outwardly through the mandrel ports 77 into the cylinder space 22. Sand, debris, and other foreign substances sometime tend to settle out and accumulate in the cylinder space 22. At times, the accumulation may be of such an extent as to tend to prevent subsequent downward movement of the body 14 along the mandrel 10 when the cutters 27 are to be shifted to their retracted position. In the present instance, such accumulations are prevented by the provision of bleeding or circulating passages 105 extending between the cylinder space 22 and the kelly passage 46 at a point below the lateral ports 77.

As specifically disclosed in the drawings, a plurality, such as a pair, of ports or passages 105 are provided which are disposed in an inclined position. The upper end 1060f each passage opens into the cylinder space 22 immediately above the upper end of the Kelly piston 19, whereas the lower end 107 of each passage 105 opens into the central passage 46 through the kelly at a point substantially below the ports 77. It is evident from the drawings, particularly from an inspection of Fig. 6, that each circulation or bleeder passage 105 is inclined in a downward and inward direction.

With such passages, it is found that foreign substances do not accumulate in the cylinder space 22. The fluid pumped down through the passage 46 and into the passage 47 builds up a back pressure in the passage 46 of a suflicient magnitude to act through the ports 77 and the inclined passages 105 on the fluid in the cylinder space 22, moving and holding the body 14 in its upward position with respect to the mandrel 10. However, the fluid flowing past the lower ends 107 of the bleeder passages 1053 creates a suction effect, inducing a reduced pressure in the passages 105 to draw fluent materials from the cylinder space 22. The pressure in the inclined passages 105 is relatively high, but it is slightly lower than the pressure in the passages or ports 77. In effect, the passages 77 may be considered as inlet passages, whereas the inclined passages 105 may be considered as outlet passages. There is some circulation of fluid from the central passage 46 of the mandrel through the ports '77 into the cylinder space 22, the fluid and other substances in the cylinder space 22 then passing down through the inclined or outlet passages 105 and back into the mandrel passage 46 at the point 107 below the ports 77, whereupon such fluid continues to be pumped downwardly through the tubular member passage 47 for discharge from the tool.

The circulation of fluid through the inlet passages 77, cylinder space 22, and outlet passages 105 continues during the drilling of the enlarged hole in the well bore, so long as fluid is being pumped down through the drill pipe B and the mandrel passages 46, 47. Such continuous circulation of fluid is effecting a constant circulation or washing action in the cylinder space 22, preventing the settling out and accumulation of harmful solid substances therein. Accordingly, the cylinder space 22 is maintained free of foreign substances, and there are no materials present in it that tend to prevent upward movement of the mandrel 10 relative to the body 14 when the cutters 27 are to be retracted.

It has been found that the provision of the circulation port and passage arrangement 77, 105 between the mandrel passage 46 and the cylinder space 22, and the provision of the circulation port arrangement 101, 102 in the body of the tool, not only prevent the parts from binding when in the well bore, thereby insuring proper operation of the tool therewithin, but it also facilitates disassembly and cleaning of the tool once it has been removed from the hole. The parts are found to be freely movable and in good condition, there being no sand accumulation either in the cylinder space 22 or between the lower portion 81, 82 of the kelly 13 and the body socket 16.

The inventor claims:

1. In a rotary drill bit: a main body; cutter means mounted on said body for expansion laterally outward of said body; means for expanding and holding said cutter means laterally outward, comprising a mandrel connectible to a drill string and having a central passage communicable with the drill string, and a cylinder on said body; said mandrel having an upper passage for feeding fluid under pressure from said central passage to said cylinder to elevate said body along said mandrel, and said mandrel having a lower passage opening into said cylinder and into said central passage below said upper passage and below the point of communication of said lower passage with said cylinder.

2. In a rotary well drilling bit: a main body; cutter means mounted on said body for expansion laterally of said body; a mandrel connectible to a drill string and slidably splined to said body, whereby drilling torque is transmitted from said mandrel to said body; said mandrel having a fluid passage communicating with the drill string; coengageable expander means on said mandrel and cutter means; hydraulically operable means on said body; means for feeding fluid under pressure from said passage into said hydraulically operable means to elevate said body and cutter means with respect to said mandrel to cause said expander means to expand said cutter means laterally outward; and means providing a second passage for fluid which opens into said hydraulically operable means and into said fluid passage below said feeding means and below the point of communication of said second passage with said hydraulically operable means.

3. In a rotary drill bit: a main body; cutter means mounted on said body for expansion laterally outward of said body; means for expanding and holding said cutter means laterally outward, comprising a mandrel connectible to a drill string and slidably splined to said body, whereby drilling torque is transmitted from said mandrel to said body; said mandrel having a central passage communicable with the drill string; hydraulically operable means on said body; said mandrel having an upper passage for feeding fluid under pressure from said central passage to said hydraulically operable means to elevate said body along said mandrel; and said mandrel having a lower passage opening into said hydraulically operable means and said central passage below said upper passage and below the point of communication of said lower passage with said hydraulically operable means.

4. In a rotary drill bit: a main body having a passage therethrough; cutter means mounted on said body for expansion laterally outward of said body; hydraulically operable means for expanding said cutter means laterally outward; first means for feeding fluid under pressure from said body passage to said hydraulically operable means; and second means for feeding fluid from said hydraulically operable means to said body passage at a point substantially below the point of communication of said first feeding means with said body passage; the point at which said second means feeds fluid from said hydraulically operable means to said body passage being substantially below the point Where said second means receives fluid from said body passage.

5. In a rotary well drilling bit: a main body; cutter means mounted on said body for expansion laterally out- Ward of said body; a mandrel connectible to a drill string and slidably splined to said body, whereby drilling torque is transmitted from said mandrel to said body; coengageable expander means on said mandrel and cutter means; said body and mandrel having companion cylinder and piston portions slidably and sealingly engaging each other to provide a cylinder space therebetween; said mandrel having a central passage communicable with the drill string and an upper passage for feeding fluid under pressure from said central passage to said cylinder and piston portion to elevate said body along said mandrel; said mandrel having a lower passage opening into said cylinder space and into said central passage below said upper passage and below the point of communication of said lower passage with said cylinder space.

6. In a rotary well drilling bit: a main body; cutter means mounted on said body for expansion laterally outward of said body; means for expanding and holding said cutter means laterally outward, said expanding and holding means comprising a mandrel connectible to a drill string and slidably splined to said body within a bore in said body; said body having a passage opening into the lower end of said bore; said body having a side port extending from the exterior of said body and opening into said bore substantially above the lower end of said bore, whereby fluid flowing through said passage into said bore can flow out through said side port.

7. In a rotary well drilling bit: a main body; cutter means mounted on said body for expansion laterally outward of said body; means for expanding and holding said cutter means laterally outward, said expanding and holding means comprising a mandrel connectible to a drill string and slidably splined to said body within a bore in said body; said body having a passage opening into the lower end of said bore; said body having an upper port extending from the exterior of said body and opening into said bore substantially above the lower end of said bore, whereby fluid flowing through said passage into said bore can flow out through said side port; said body having a lower port extending from the exterior of said body and opening into said bore substantially at the lower end of said bore, whereby fluid can circulate from one of said ports through said bore and through said other port.

8. In a rotary well drilling bit: a main body; cutter means mounted on said body for expansion laterally outward of said body; a mandrel connectible to a drill string and slidably splined to said body, whereby drilling torque is transmitted from said mandrel to said body; coengageable expander means on said mandrel and cutter means; said body and mandrel having companion cylinder and piston portions slidably and sealingly engaging each other to provide a cylinder space therebetween; said mandrel having a fluid passage communicating with the drill string and cylinder space to feed fluid under pressure into said cylinder space to elevate said body and cutter means with respect to said mandrel to cause said expander means to expand said cutter means laterally outward; said body having a side port opening to the exterior of said body and into a region between said mandrel and body below said piston portion.

9. In a rotary well drilling bit: a main body; cutter means mounted on said body for expansion laterally outward of said body; a mandrel connectible to a drill string and slidably splined to said body, whereby drilling torque is transmitted from said mandrel to said body; coengageable expander means on said mandrel and cutter means; said body and mandrel having companion cylinder and piston portions slidably and sealingly engaging each other to provide a cylinder space therebetween; said mandrel having a fluid passage communicating with the drill string and cylinder space to feed fluid under pressure into said cylinder space to elevate said body and cutter means with respect to said mandrel to cause said expander means to expand said cutter means laterally outward; said body having an upper port opening to the exterior of said body and into a region between said mandrel and body below said piston portion; said body having a lower port opening to the exterior of said body and into said region substantially below said upper port, whereby fluid can circulate from one of said ports through said region and through said other port.

10. In a rotary well drilling bit: a main body; cutter means mounted on said body for expansion laterally outward of said body; a mandrel connectible to a drill string and slidably splined to said body within a bore in said body; said body having a passage opening into the lower end of said bore; said mandrel having a fluid passage communicating with the drill string; coengageable expander means on said mandrel and cutter means; hydraulically operable means on said body; means for feeding fluid under pressure from said fluid passage into said hydraulically operable means to elevate said body and cutter means with respect to said mandrel to cause said expander means to expand said cutter means laterally outward; means providing a second passage for fluid which opens into said hydraulically operable means and into said fluid passage below said fluid feeding means and below the point of communication of said second passage with said hydraulically operable means; said body having a side port opening into said bore substantially above the lower end of said bore.

11. In a rotary well drilling bit: a main body; cutter means mounted on said body for expansion laterally outward of said body; a mandrel connectible to a drill string and slidably splined to said body, whereby drilling torque is transmitted from said mandrel to said body; said mandrel having a fluid passage communicating with the drill string; coengageable expander means on said mandrel and cutter means; said body and mandrel having companion cylinder and piston portions slidably and sealingly engaging each other to provide a cylinder space therebetween; said mandrel having an upper passage for feeding fluid under pressure from said fluid passage to said cylinder space to elevate said body along said mandrel; said mandrel having a lower passage opening into said cylinder space and into said fluid passage below said upper passage and below the point of communication of said lower passage with said cylinder space; said body having a side port opening to the exterior of said body and into a region between said mandrel and body below said piston portion.

12. In a rotary well drilling bit: a main body; cutter means mounted on said body for expansion laterally outward of said body; a mandrel connectible to a drill string and slidably splined to said body, whereby drilling torque is transmitted from said mandrel to said body; said mandrel having a fluid passage communicating with the drill string; coengageable expander means on said mandrel and cutter means; said body and mandrel having companion cylinder and piston portions slidably and sealingly engaging each other to provide a cylinder space therebetween; said mandrel having an upper passage for feeding fluid under pressure from said fluid passage to said cylinder space to elevate said body along said mandrel; said mandrel having a lower passage opening into said cylinder space and into said fluid passage below said upper passage and below the point of communication of said lower passage with said cylinder space; said body having an upper port opening to the exterior of said body and into a region between said mandrel and body below said piston portion; said body having a lower port opening to the exterior of said body and into said region substantially below said upper port.

13. in a rotary drill bit: a main body; cutter means mounted on said body for expansion laterally outward of said body; means for expanding and holding said cutter means laterally outward, comprising a mandrel connectible to a drill string and slidably splined to said body whereby drilling torque is transmitted from said mandrel to said body; said mandrel having a central passage communicable with the drill string; hydraulically operable means on said body; said mandrel having an upper passage for feeding fluid under pressure from said central passage to said hydraulically operable means to elevate said body along said mandrel; and said mandrel having a lower passage inclined in a downward direction toward the axis of said mandrel and opening at its upper end into said hydraulically operable means and at its lower end into said central passage below said upper passage.

14. In a rotary drill bit: a main body having a passage therethrough; cutter means mounted on said body for expansion laterally outward of said body; hydraulically operable means for expanding said cutter means laterally outward; first means for feeding fluid under pressure from said body passage to said hydraulically operable means; and second means for feeding fluid from said by draulically operable means to said body passage, said second means being inclined in a downward direction toward the axis of said body and opening at its upper end into said hydraulically operable means and at its lower end into said body passage at a point substantially below the point of communication of said first feeding means with said body passage.

References (Cited in the file of this patent UNITED STATES PATENTS 1,908,594 Foster May 9, 1933 2,482,674 Kriegel Sept. 20, 1949 2,751,013 Conrad June 19, 1956 2,755,070 Kammerer July 17, 1956 

